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Commit c5a50529 authored by Bernhard Froemel's avatar Bernhard Froemel Committed by Matthew Garrett
Browse files

apple-gmux: Fix index read functions 



Study of Apple's binary driver revealed that the GMUX_READ_PORT should
be written between calls to gmux_index_wait_ready and
gmux_index_wait_complete (i.e., the new index protocol must be
followed). If this is not done correctly, the indexed
gmux device only partially accepts writes which lead to problems
concerning GPU switching. Special thanks to Seth Forshee who helped
greatly with identifying unnecessary changes.

Signed-off-by: default avatarBernhard Froemel <froemel@vmars.tuwien.ac.at>
Signed-off-by: default avatarMatthew Garrett <mjg@redhat.com>
parent 07f377da

drivers/platform/x86/apple-gmux.c

+4 −2
Original line number Diff line number Diff line
@@ -142,8 +142,9 @@ static u8 gmux_index_read8(struct apple_gmux_data *gmux_data, int port) 
	u8 val;



	mutex_lock(&gmux_data->index_lock);

	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);

	gmux_index_wait_ready(gmux_data);

	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);

	gmux_index_wait_complete(gmux_data);

	val = inb(gmux_data->iostart + GMUX_PORT_VALUE);

	mutex_unlock(&gmux_data->index_lock);
@@ -166,8 +167,9 @@ static u32 gmux_index_read32(struct apple_gmux_data *gmux_data, int port) 
	u32 val;



	mutex_lock(&gmux_data->index_lock);

	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);

	gmux_index_wait_ready(gmux_data);

	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);

	gmux_index_wait_complete(gmux_data);

	val = inl(gmux_data->iostart + GMUX_PORT_VALUE);

	mutex_unlock(&gmux_data->index_lock);